Nanotechnology: Turning Nanoscience Into Nanomanufacturing

The concept of nanotechnology is now firmly embedded in modern culture. It is seen as the source of potentially dramatic advances in almost every field imaginable, including energy, health, the environment, defense and, of course, electronics. President Bush declared it a priority in 2006, as have CEOs of companies such as General Electric and Proctor & Gamble.

By 2014, according to a recent report from Lux Research (New York, N.Y.), $2.6T in global manufactured goods will incorporate nanotechnology, or ~15% of total output.¹ The research firm stated that governments, corporations and venture capitalists spent $9.6B on nanotechnology R&D worldwide in 2005, up 10% from 2004. Another Lux Research report released in November estimated that venture capitalist investments in nanotech start-ups will reach $650M in 2006, and the average deal was $11.5M, 19% higher than 2005's $9.6M.² Ten venture-backed nanotech start-ups have managed an IPO of shares, raising an aggregate $417.2M at their debuts with a total implied valuation of $1.69B.

The original concept of nanotechnology was first described by Richard Feynman in 1959 in a now famous address at the California Institute of Technology (Pasadena, Calif.) to the American Physical Society.³ The comments made by Feynman are interesting in that he clearly differentiated between controlling things on a small scale and miniaturization.⁴ “In the year 2000, when they look back at this age, they will wonder why it was not until the year 1960 that anybody began seriously to move in this direction,” he said.

Carbon nanotubes are a cornerstone of nanotechnology because of their superior electrical, mechanical and thermal properties. This simulated image is a result of work done to understand how nanotubes deform. (Source: IBM)

“Nanoscale phenomena and objects have been around for some time. Catalysts, for example, are mostly nanoscale particles, and catalysis is a nanoscale phenomenon. Photography is another example of nanoscale technology. Most of molecular biology works at nanoscale,” Wong said. “What is new and different now is the degree of understanding and deliberate control and precision that the new nanoscale techniques afford. Instead of discovering new phenomena by accident or by random search, we can look for them systematically. Instead of finding nanoscale particles and structures with good properties through serendipity, we now seek to design them to order. Furthermore, novel structures and fundamentally new properties and processes can be obtained. We are witnessing an explosion of revolutionary discoveries at nanoscale.”

What's particularly intriguing is that some well known materials act quite differently at the nanoscale. Opaque substances become transparent (copper), inert materials become catalysts (platinum), stable materials turn combustible (aluminum), and solids turn into liquids at room temperature (gold). Gold, which is chemically inert at normal scales, is also interesting in that it can serve as a potent chemical catalyst at the nanoscale.

The second silicon revolution

1. The ‘quantum mirage’ effect relies on the wave nature of electrons instead of conventional wiring to enable data transfer within nanoscale electronic circuits too small to use wires. To create the quantum mirage, the scientists first moved several dozen cobalt atoms on a copper surface into an ellipse-shaped ring. The ring atoms act as a ‘quantum corra’ — reflecting the copper’s surface electrons within the ring into a wave pattern predicted by quantum mechanics. (Source: IBM)

The first nanotube-based transistors appeared in 1998, followed by IBM's (Yorktown Heights, N.Y.) discovery of the “quantum mirage” effect in 2000 (Fig. 1), which employed the wave nature of electrons instead of conventional wiring to enable data transfer within nanoscale electronic circuits too small to use wires. Other notable milestones that enabled nanotechnology as we know it today were the development of the atomic force microscope in 1985 and the discovery of carbon nanotubes (CNTs) in 1991. Functional logic circuits and a ring oscillator built from discrete nanotube transistors first appeared in 2001, and the world's smallest solid-state light emitter built on a CNT appeared in 2003 (Fig. 2). In 2005, using DNA molecules as scaffolds, scientists at the University of Illinois at Urbana-Champaign created superconducting nanodevices that demonstrated a new type of quantum interference (Fig. 3). 2006 saw the demonstration of a five-stage, 10-transistor ring oscillator built as an IC on a single nanotube,⁵ and the introduction of the nano­SQUID, a superconducting quantum interference device made with CNTs.⁶

2. A CNT’s applicability to optoelectronics was demonstrated by light emission from a single nanotube, 1.4 nm in diameter. (Source: IBM)

Nanoscience vs. nanomanufacturing

3. Using DNA molecules as scaffolds, scientists at the University of Illinois created superconducting nanodevices that demonstrated a new type of quantum interference, as shown in this artist’s interpretation. (Source: University of Illinois)

David Berube, professor of communication studies at the University of South Carolina (Columbia, S.C.) and the associate director of nanoscience and technology studies at the USC NanoCenter, has authored a book titled Nano-Hype: The Truth Behind the Nanotechnology Buzz.⁸ He concluded that much of what is sold today as “nanotechnology” is in fact a recasting of straightforward materials science, which is leading to a “nanotech industry built solely on selling nanotubes, nanowires and the like,” which will “end up with a few suppliers selling low-margin products in huge volumes.”

Indeed, CNTs can be purchased “off-the-shelf” from more than 65 suppliers,⁹ or they can be synthesized by various methods including arc-discharge, laser ablation and chemical vapor deposition (CVD). CVD is the most suitable for controlling the synthesis of CNTs on substrates¹⁰ for the same reason it is commonly used in mainstream semiconductor manufacturing. CNTs have been the focus of such a remarkable amount of development because of their superior electrical, mechanical and thermal properties (although there are also unique advantages associated with other types of nanostructures, notably nanowires and quantum dots).

In the electronics world, only a few products made with CNTs are now available. Some early CNT sensors, probe tips and transparent conductive films are on the market, with more developed versions soon to come. Developers also now say more complex CNT-based memory chips, field emission devices and thermal management materials could be available within the next few years.⁹ Most off-the-shelf CNTs are instead going into what you might call novel applications. The world's first sailboat mast using CNTs, for example, was unveiled at the nanoTX '06 tradeshow in Dallas in October by CNT maker Zyvex Corp. (Richardson, Texas). The company said the mast made with its NanoSolve materials would improve yacht performance by significantly increasing the strength and stiffness of the mast without adding weight.

The most promising applications of CNTs are those involving use in electron emission devices and nanoelectronics, such as field effect transistors, nanotube transistors, nanotube interconnects and nanosensors.¹⁰ Why? CNTs can withstand high current density (10⁹ A/cm²) and ballistic conductance by virtue of their 1-D electronic structure. Before CNTs and other nanostructures can be successfully implemented in mainstream manufacturing, their fabrication will have to be controllable.

In the Nanomanufacturing Handbook,¹⁰ Northeastern University's (Boston) Ahmed Busnaina makes an important distinction between nanoscience and nanomanufacturing. “Scientific breakthroughs in nanoscience have come at a surprisingly rapid rate over the past few years. The transfer of nanoscience accomplishments into technology, however, is severely hindered by a lack of understanding of barriers to manufacturing in the nanoscale dimension. For example, while shrinking dimensions hold the promise of exponential increases in data storage densities, realistic commercial products cannot be realized without first answering the question of how one can wire millions and billions of nanoscale devices together, or how one can prevent failures and avoid defects,” he said. “Most nanotechnology research focuses on surface modification, manipulating several to several hundred particles or molecules to be assembled into desirable configurations. There is a need to conduct massive direct assembly of nanoscale elements at high rates and over large areas. To move scientific discoveries from the laboratory to commercial products, a completely different set of fundamental research issues must be addressed — primarily those related to viable commercial scale-up of production volumes, process robustness and reliability, and integration of nanoscale structures and devices into micro-, meso- and macro-scale products.”

A disconnect between nanoresearch and what's required for production manufacturing is also found in the Emerging Research Device “Difficult Challenges” section of the International Technology Roadmap for Semiconductors (ITRS).¹¹ It states, “Nanostructure materials such as carbon nanotubes (CNTs) or molecules must be assembled in defined locations with controlled orientation and reproducible properties (CNTs grow in random locations with random orientations). Molecules only self-organize on a small number of material surfaces and require thiol functionalization for assembly on Au [gold] and defect formation is not understood.

“Similar challenges exist for nanodevices, such as spin transistors. Materials with strongly correlated electron states have unique complex interactions between electric and magnetic properties, with complex ferromagnetic to antiferromagnetic phase transitions that may support spontaneous spin precipitation. The challenge is to determine whether these properties can be used to enable new devices at the nanometer scale.”